Methods and systems for automatic rotation direction determination of electronically commutated motor

ABSTRACT

A method for determining a direction of rotation for an electronically commutated motor (ECM) is described. The motor is configured to rotate a blower and the method comprises rotating the blower using the ECM and determining if the resulting blower rotation is indicative of the desired direction of rotation for the blower.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/142,136, filed May 31, 2005 now U.S. Pat. No. 7,573,217, which ishereby incorporated by reference and is assigned to the assignee of thepresent invention.

BACKGROUND OF THE INVENTION

This invention relates generally to electronically commutated motors(ECMs), and more particularly, to methods and systems for automaticdetermination of a rotation direction within electronically commutatedmotors.

Electronically commutated motors (ECMs) are used in a wide variety ofapplications because they are more efficient than known standardinduction motors. ECMs include the efficiency and speed controladvantages of a DC motor and minimize the disadvantages of DC motors,e.g., carbon brush wear, short life span, and noise. In Heating,Ventilation and Air Conditioning (HVAC) systems, as well as, knowncommercial air distributions systems, ECMs automatically adjust blowerspeed to meet a wide range of airflow requirements. Known ECMs usemicroprocessor technology to control fan speed, torque, air flow, andenergy consumption.

As described above, ECM motors are generally utilized in air handling(blowers, fans) applications within HVAC systems. Blower wheels andhousings are used in right and left hand configurations, i.e. clockwiseand counter clockwise rotation. To minimize the motor models required byan OEM (Original Equipment Manufacturer) it is desirable to utilize asingle motor to serve both blower rotation directions. Such a motorwould also reduce errors caused by using several motor models whenchanging from a standard induction motor to an ECM. However, such amotor would also have a capability to detect the proper rotationdirection for the blower in which it has been installed.

It is believed that some systems observe a coast-down of the blower todetermine some data associated with a load for that blower which is thenused to determine settings to be used in producing constant airflow. Inother motor drives, the direction of rotation is changed either throughcommunication to a motor drive computer or by changing the setting of aswitch or placement of a jumper wire.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method for determining a direction of rotation for anelectronically commutated motor (ECM), where the motor is configured torotate a blower is provided. The method comprises rotating the blowerusing the ECM, measuring a speed of the blower for a predefined level oftorque, and determining if the measured speed and applied torque areindicative of the desired direction of rotation for the blower.

In another aspect, a method for determining a direction of rotation foran electronically commutated motor (ECM), where the motor is configuredto rotate a blower is provided. The method comprises rotating the blowerusing the ECM, applying an amount of torque necessary to rotate theblower at a predefined speed, and determining if the predefined speedand applied torque are indicative of the desired direction of rotationfor the blower.

In yet another aspect, an air moving control system is provided thatcomprises a blower, an electronically commutated motor (ECM), and acontroller. The ECM is configured to rotate the blower and thecontroller is configured to control rotation of the motor. Thecontroller is further configured to determine if a direction of rotationof the ECM is the same as the desired direction of rotation of theblower.

In still another aspect, a control system configured to controloperation of an electronically commutated motor (ECM) attached to ablower is provided. The control system comprises a motor controllerconfigured to control a direction of rotation of the ECM and furtherconfigured to cause the ECM to rotate at one of a selected level oftorque and a predefined speed. The control system further comprises asystem controller configured to receive data relating to the amount oftorque applied to the motor and a speed of rotation of at least one ofthe motor and the blower. The system controller is further configured todetermine if a direction of rotation of the ECM is the same as thedesired direction of rotation for the blower and instruct the motorcontroller to change the direction of rotation of the motor if thedetermination is negative.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an air moving control system including anelectronically commutated motor (ECM) and a blower.

FIG. 2 is a flowchart illustration of a method for determining if therotation of the ECM and blower at a predefined speed is in the desireddirection of rotation.

FIG. 3 is a flowchart illustration of a method for determining if therotation of the ECM and blower at a selected level of torque is in thedesired direction of rotation.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram of an air moving control system 10 used tocontrol an electronically commutated motor (ECM) 12. System 10 is an airmoving control system, such as a residential heating, ventilation andair conditioning (HVAC) control system, a light industrial HVAC controlsystem, or a clean room filtering control system. System 10 includes aninterface circuit 14 electrically coupled to a system controller 16, forexample a HVAC system controller, and a main unit 18, for example a HVACunit. Main unit 18 includes components 20 and ECM 12. In one embodiment,ECM 12 is a motor configured to rotate a blower. Motor 12 includes amotor controller 22 including a microprocessor (not shown) and a memory(not shown) containing an ECM program. In one embodiment, systemcontroller 16 is connected to a thermostat 24. Thermostat 24 includes aplurality of settings, or modes, such as low heat, high heat, cooling,dehumidify, and continuous fan. Additionally, thermostat 24 measures atemperature in a predetermined space or location and transmits anelectrical signal representing the measured temperature to controller16.

Controller 16 controls main unit 18 via interface circuit 14. Interfacecircuit 14 receives control signals in the form of input voltage signalsfrom system controller 16 and translates the signals to signals suitablefor controlling by ECM 12. Typically, circuits within system 10 operateat a different voltage level than does ECM 12. Therefore interface 14 isutilized for communications between controller 16 and ECM 12. Suchinterfaces typically control ECMs using pulse width modulation (PWM) bycontinuously adjusting motor speed.

The translated signals are transmitted to motor controller 22 of ECM 12,and a torque of ECM 12 is varied in accordance with the adjusted voltageoutputs. ECM 12 is mechanically connected to a blower 28. In oneembodiment, blower 28 includes a detection module 30 which providessignals, for example signals indicative of a speed of rotation of blower28, to system controller 16. In one embodiment, blower 28 is a forwardcurved centrifugal blower.

System 10 is configured to automatically determine a proper direction ofrotation for ECM 12. As used herein, the proper direction of rotationfor a blower is the direction of rotation that causes the desiredairflow through, for example, the HVAC system. Once the correctdirection of rotation is determined, it is stored within the memory ofmotor controller 22 such that ECM will rotate in the proper (desired)direction upon subsequent applications of power. In certain embodiments,for example, a forward curved centrifugal blower, a curvature of theblades of blower 28 is such that blower 28 produces useful work in onedirection only. As described above, ECM 12 is attached to blower 28. Fora blower (e.g., blower 12), the load curve for a forward, or proper,direction of rotation is markedly different, than the load curve forreverse rotation. Specifically, a much higher torque, for a givenrotation speed, must be applied to blower 28 for rotation in the properdirection. Once such a torque determination is made, the direction ofrotation which resulted in the higher torque is stored within motorcontroller 22.

System 10 is configured to determine the proper direction of rotationfor ECM 12. In one embodiment, system controller 16 and motor controller22 are configured to cause ECM 12 to rotate at a set level of torque.Detection module 30 senses rotation, and a speed of rotation, of blower28. Once ECM 12 is operating at the set level of torque, systemcontroller 16 senses the speed of rotation of blower 28, and determinesif the measured speed is a speed consistent for the applied torquelevel. If so, then ECM 12 (and blower 28) are rotating in the properdirection and the direction of rotation is stored within motorcontroller 22. If the resultant speed is too great, then it isdetermined that ECM 12 (and blower 28) are rotating in a directionopposite the desired direction, and the opposite direction of rotationis stored within motor controller 22 and is accessed during subsequentapplications of power to ECM 12.

In an alternative embodiment, ECM 12 (and blower 28) are powered up torotate at a selected speed. The speed can be measured utilizing eitherdetection module 30 or motor controller 22. If the torque required toreach such a rotation speed is less than expected, ECM 12 (and blower28) are not rotating in the desired direction and motor controller 22memory is updated accordingly to ensure that ECM 12 is rotated in thecorrect direction when power is subsequently applied.

In another embodiment, controller 22 is configured to rotate ECM 12 (andblower 28) a small amount in each direction, such as one or tworevolutions. Using detection module 30, the deceleration rates of blower28 are observed when current is removed from ECM 12. The decelerationrates taken when passing through a given speed for each direction ofrotation are compared, and the direction of rotation having the highestdeceleration rate becomes the desired direction of rotation and isstored as such within the memory of motor controller 22. Alternatively,either or both of speeds and applied torque in each direction can becompared to determine the desired direction of rotation. Once thecomparison is made and determination of the desired direction ofrotation is completed, data indicative of the desired direction ofrotation is stored within the memory of motor controller 22.

For any of the above described embodiments, the direction of rotationtesting will be performed only on an initial power up of ECM 12, sincethe desired direction of rotation is stored in memory (e.g., memorywithin system controller 16 or within the memory associated with motorcontroller 22) for all following start ups of ECM 12. Since ECM 12 isintended to be continuously powered, the reoccurrence of the abovedescribed blower direction testing will be very infrequent.

FIG. 2 is a flowchart 50 illustrating a method for determining if therotation of the ECM (such as ECM 12 shown in FIG. 1) and the blower(such as blower 28 shown in FIG. 1) at a predefined speed is in thedesired direction of rotation. The blower is rotated 52 with the ECM ata predefined speed. The torque required to maintain the predefined speedis then measured 54. It is then determined 56, for example within systemcontroller 16 (shown in FIG. 1), whether the torque needed to maintainthe predefined speed is indicative of the desired direction of rotation.As described above, if the torque needed to maintain the desired speedis below an expected value, based on known characteristics of theblower, then the motor is rotating in a direction opposite the desireddirection of rotation Once determination 56 of desired motor directionof rotation is complete, the data indicative of the desired direction ofrotation for the motor is stored 58 within the motor controller.

FIG. 3 is a flowchart 70 illustrating a method for determining if therotation of the ECM (such as ECM 12 shown in FIG. 1) and blower (such asblower 28 shown in FIG. 1) at a selected level of torque is in thedesired direction of rotation. The blower is rotated 72 with the ECM ata selected level of torque. The speed of the blower (or motor) ismeasured 74. It is then determined 76, for example within systemcontroller 16 (shown in FIG. 1), whether the speed resulting from theselected level of torque is indicative of the desired direction ofrotation. As described above, if the speed resulting from a selectedlevel of torque is above an expected value, based on knowncharacteristics of the blower, then the motor is rotating in a directionopposite the desired direction of rotation. Once determination 76 ofdesired motor direction of rotation is complete, the data indicative ofthe desired direction of rotation for the motor is stored 78 within themotor controller.

As described above, electronically commutated motors are typically usedin air handling applications, for example, providing rotation to blowersand fans in HVAC systems. Known blower wheels and housings are found inboth right hand and left hand configurations (clockwise andcounter-clockwise rotation) Using the methods and system abovedescribed, a user is able to minimize the number of different motormodels needed to serve both blower rotation directions as the motorcontrol system is able to detect the proper rotation direction that forthe blower it is to drive. Therefore, the automatic detection ofrotation direction and storage within the motor controller of thedesired direction of rotation for subsequent power ups features providemotor model inventory reduction. Also, the feature results in areduction or elimination of instances where the wrong direction ofrotation motor is installed with a blower, thereby reducing productionline failures at an OEM.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A control system operable with an air moving device, said controlsystem comprising: an electronically commutated motor (ECM) configuredto rotate a blower; and a motor controller configured to controlrotation of said ECM and further configured to operate said ECM at apredefined level of torque and to compare a measured speed of rotationof at least one of said ECM and the blower to a predefined speed ofrotation associated with the predefined level of torque to determine ifa direction of rotation of said ECM corresponds to a predefineddirection of rotation of the blower.
 2. A control system according toclaim 1 wherein said motor controller is configured to receive a speedof rotation measurement from the blower.
 3. A control system accordingto claim 1 wherein said motor controller is configured to change adirection of rotation of said ECM if the determined direction ofrotation is not the predefined direction of rotation.
 4. A controlsystem according to claim 1 wherein said motor controller is configuredto store data associated with the predefined direction of rotation.
 5. Acontrol system according to claim 1 wherein the blower comprises aforward curved centrifugal blower.
 6. A control system operable with anair moving device, said control system comprising: an electronicallycommutated motor (ECM) configured to rotate a blower; and a motorcontroller configured to control rotation of said ECM and furtherconfigured to operate said ECM at a predefined speed of rotation and tocompare a level of torque required to operate said ECM at the predefinedspeed of rotation to a predefined level of torque associated with thepredefined speed of rotation to determine if a direction of rotation ofsaid ECM corresponds to a predefined direction of rotation of theblower.
 7. A control system according to claim 6 wherein said motorcontroller is configured to change a direction of rotation of said ECMif the determined direction of rotation is not the predefined directionof rotation.
 8. A control system according to claim 6 wherein said motorcontroller is configured to store data associated with the predefineddirection of rotation.
 9. A control system operable with an air movingdevice, said control system comprising: an electronically commutatedmotor (ECM) configured to rotate a blower; and a motor controllerconfigured to control rotation of said ECM and further configured to:rotate the blower for a length of time in a first direction; removecurrent from said ECM; receive measurements relating to a firstdeceleration rate of the blower; rotate the blower for the same lengthof time in a second direction, the second direction opposite the firstdirection; remove current from said ECM; receive measurements relatingto a second deceleration rate of the blower; and determine whether thefirst deceleration rate or the second deceleration rate is indicative ofa predefined direction of rotation of the blower.
 10. A control systemaccording to claim 9 wherein said motor controller is configured tostore the direction of rotation associated with the greater of the firstmeasured deceleration rate and the second measured deceleration rate asthe direction of rotation that corresponds to the predefined directionof rotation of the blower.
 11. A method for configuring an air movingsystem that includes a motor controller and an electronically commutatedmotor (ECM) configured to rotate a blower based on commands received bythe motor controller, said method comprising: storing, in the motorcontroller, an expected value for at least one of a torque applied torotate the blower at a predefined speed and an expected speed ofrotation of the blower obtained by applying a predefined level oftorque, wherein the expected value corresponds to rotation of the blowerin a predefined direction; rotating the ECM to operate the blower inaccordance with predefined criteria, the predefined criteria includingone of the predefined speed and the predefined level of torque;measuring an operating value, the operating value including at least oneof an actual speed of rotation of the blower and an actual torqueapplied to the ECM; and comparing the operating value to the expectedvalue to determine if a direction of rotation of the ECM corresponds tothe predefined direction of rotation for the blower.
 12. A method inaccordance with claim 11 further comprising storing data indicative ofthe predefined direction of rotation for the ECM once it is determinedthat the direction of rotation of the ECM corresponds to the predefineddirection of rotation for the blower.
 13. A method in accordance withclaim 11, wherein comparing the operating value to the expected valuecomprises determining that the direction of rotation of the ECMcorresponds to the predefined direction of rotation for the blower whenthe measured operating value corresponds to the expected value.
 14. Amethod in accordance with claim 11, wherein comparing the operatingvalue to the expected value comprises determining that the direction ofrotation of the ECM does not correspond to the predefined direction ofrotation for the blower when the actual torque applied to the ECM tomaintain the predefined speed is below the expected torque value.
 15. Amethod in accordance with claim 11, wherein comparing the operatingvalue to the expected value comprises determining that the direction ofrotation of the ECM does not correspond to the predefined direction ofrotation for the blower when the actual speed of rotation of the blowerobtained by applying the predetermined level of torque is higher thanthe expected speed of rotation of the blower.
 16. A control systemoperable with an air moving device, said control system comprising: anelectronically commutated motor (ECM) configured to rotate a blower; anda motor controller configured to control rotation of said ECM andfurther configured to: rotate said ECM in a first direction at apredefined level of torque; receive measurements relating to a firstspeed of at least one of said ECM and the blower; rotate said ECM in asecond direction, opposite the first direction, at the predefined levelof torque; receive measurements relating to a second speed of at leastone of said ECM and the blower; and determine whether the first speed orthe second speed is indicative of a predefined direction of rotation ofthe blower.
 17. A control system in accordance with claim 16, said motorcontroller further configured to compare the first speed and the secondspeed, wherein a lower speed corresponds to the predefined direction ofrotation of the blower.
 18. A control system according to claim 16wherein said motor controller is configured to store data associatedwith the predefined direction of rotation.
 19. A control systemaccording to claim 16 wherein the blower comprises a forward curvedcentrifugal blower.